Sciencemadness Discussion Board

30% HCl found to be 17.3%??

Fantasma4500 - 23-2-2013 at 06:49

so today i got 250g K2CO3 home, decided i would make some KCl out of it..
so as i trust my bottles of HCl saying 30% arent lying i measure out 69g K2CO3 and 52.5 mL 30% HCl

i mix them up diluted and then i leave for a while as i have finished adding the HCl to the K2CO3
so i decide that it might need some more HCl as i remember it still bubbled violently when adding HCl even at the end, which it shouldnt do if i added correct molar amounts..

K2CO3 + 2HCl > 2KCl + H2CO3

i used 1:1 molar ratio, because i forgot that it was K2CO3 and not KCO3
now onto the part that blows my mind..

im not sure if i used twice the amount of HCl, but i sure added alot
as i still havent realised at this point that i used wrong molar ratios, i decided to weight 50 mL 30% HCl
i got 50 mL to 52.25g
that would be only 5 moles aka 17.3%???

there couldnt be much more than 50 mL left in the first bottle, i added about 5-10 mL extra to the still reacting K2CO3 solution from a completely new HCl bottle, which i weighted the weight of, of 50 mL

i realise i should have used 105 mL HCl instead of 52.5 mL, but again, weighting the HCl, in short just doesnt make sense, it reacted as if it was 30% HCl, but when weighted it showed the weight of 17.3% HCl?

i was using a very accurate 0.01g - 100g weight
the HCl is fuming and have a strong yellow colour

blogfast25 - 23-2-2013 at 07:02

If it's fuming, it's likely to be > 30 %.

I've had problems in the past with hardware store HCl being much less concentrated than advertised on the bottle. But I used proper acidometry (titration) to determine HCl content.

The density ("specific gravity") of 30 % HCl is 1.15 g/ml, so if you accurately weigh a 100 ml of your product you can work it out, it should weigh about 115 g. At 37 % (max. conc.) it should weigh 118.5 g.

The yellow is caused by FeCl3: using that grade means you'll find iron in whatever you use it for (your KCl for instance will have a brown/reddish hue). But strong yellow is also an indication the HCl is quite concentrated.



[Edited on 23-2-2013 by blogfast25]

Fantasma4500 - 23-2-2013 at 07:57

well i have some sort of a problem, as i cant go past 100g, so i did 50 mL instead, then i could just double it up easily.. 52.25 x 2 = 104.50

but still, this is what doesnt make sense!!
100% sure my weight couldnt have measured wrong more than 0.1 grammes, but that many grammes is impossible.
i guess i might never find out why calculating it by weight doesnt show it properly, as molarity cant be wrong..

i guess you could call it titration, what i did to create KCl.. just not that accurate, but it was very close to 1 mole HCl used..

didnt know there was iron in it.. thanks.. but iron chloride, shouldnt that be possible to remove that by letting it dry out, where it would go into Fe2O3 and Cl2 at some point?

i have let my NH4OH 25% react to remove some gas, i got the gas by reacting the residue of blackpowder with 70% H2SO4 and then boiling it, unsure if it was SO3, but now there is some weird white precipitate in the beaker i had ammonia, i find it hard to believe the SO3 or what it could of been went into the beaker and made solid insoluble stuff..

blogfast25 - 23-2-2013 at 08:21

Quote: Originally posted by Antiswat  



didnt know there was iron in it.. thanks.. but iron chloride, shouldnt that be possible to remove that by letting it dry out, where it would go into Fe2O3 and Cl2 at some point?



1.05 SG would put the concentration at about 11 %. That's not very consistent with the observed fuming, though.

11 % HCl is about 3.2 M (mol/L). 69 g of K2CO3 is 0.5 mol and needs 1 mol of pure HCl, so about 312 ml of 3.2 M HCl.

As your product dries the FeCl3 will hydrolyse to Fe(OH)3 (the Cl elutes as HCl), which on drying becomes Fe2O3.

zed - 23-2-2013 at 15:44

All things being equal. For a couple of bucks, you can buy 4oz of KCl at the supermarket. Comes in a small blue container, labeled "No Salt".

hyfalcon - 24-2-2013 at 03:34

KCl is also found in salt free softener pellets for water softeners. Home Depot has plenty.

Fantasma4500 - 9-3-2013 at 16:57

Quote: Originally posted by blogfast25  
Quote: Originally posted by Antiswat  



didnt know there was iron in it.. thanks.. but iron chloride, shouldnt that be possible to remove that by letting it dry out, where it would go into Fe2O3 and Cl2 at some point?



1.05 SG would put the concentration at about 11 %. That's not very consistent with the observed fuming, though.

11 % HCl is about 3.2 M (mol/L). 69 g of K2CO3 is 0.5 mol and needs 1 mol of pure HCl, so about 312 ml of 3.2 M HCl.

As your product dries the FeCl3 will hydrolyse to Fe(OH)3 (the Cl elutes as HCl), which on drying becomes Fe2O3.



no definately it wouldnt seem to be 11%.. not with the fuming and all.. (:
i could try using titration on it some day, but i would need to use pipette..
i have also seen that when mixing HNO3 and NH4OH with proper amounts right after mixing and abit after theres no need for more NH4OH added (no HNO3 leftover, ammonia bottle held over produces no fumes) but then later on while cooking it down it suddenly starts craving more NH4OH..
and after that even more..
solution? excess NH4OH.

Fantasma4500 - 9-3-2013 at 17:00

nope guys.. you should try europe for a few days.. :P we just have something against potassium chloride, or well for some reason were not that much for potassium chloride..
25g K2CO3 where i live costs about 1 dollar
and you buy it in 25g bags, so i decided to buy much larger amounts online nearly 10% the price in my country.. should of done it from start..
actually ive seen some salt called ''seltin salt'' it contains 40% KCl, but what use would there be in that if you want pure anyways..